Re: It is a salvage mission in international waters, China should take over the search
"It took 5 years, and serious effort to find the Air France crash in the South Atlantic. And that yielded really useful information about how modern fly-by-wire systems create some problems."
I fully agree with you there.
The difference is that AFAIR we suspected that the pilot or the aircraft encountered some unexpected issue which we could learn from. And we did. Neither do I rule out completely that their isn't some useful knowledge lying at the bottom of the Indian Ocean. But there are not infinite resources available so a decision on whether to continue the search has to be made in advance on the balance of probabilities - since AF447 recovery cost a small fortune. Which of those would you have funded the most?
Similarly the (lesser) expense on MH17 where no problem with the airframe/engines/pilots was suspected was almost entirely justified on attempting to point the finger at who fired the missile. Again a useful result (even if it is never going to be accepted by the guilty).
The drive to find AF447 & and what hit MH17 was forensic. The drive to re-open the search appears to be coming solely for the emotional relief of know where the bodies are. That adds nothing to future aircraft safety or crimes against humanity. Only to human happiness.
Or more precisely lessen unhappiness. If that's what you want to lessen in China or Malaysia there should be more effective ways of doing that - though it sadly may be that it would be another group of unhappy/starving/sick people that would benefit. And not be reported on worldwide.